The Australian prime minister, Julia Gillard, stumbled and was caught by a security guard as riot police helped her force a path through a crowd of rowdy protesters following a ceremony to mark Australia Day.

About 200 supporters of indigenous rights surrounded a Canberra restaurant and banged its windows on Thursday while Gillard and the opposition leader, Tony Abbott, were inside officiating at an awards ceremony.

About 50 police escorted the political leaders from a side door to a car. Gillard stumbled, losing a shoe. Her personal security guard wrapped his arms around her and supported her to the waiting car, shielding her from the angry crowd.

The protesters had been demonstrating for indigenous rights nearby at the Aboriginal Tent Embassy, a collection of tents and temporary shelters on the lawn of Old Parliament House in the national capital that has become a focus for protests against Australia Day.

Australia Day marks the arrival of the first fleet of British colonists and convicts in Sydney on 26 January 1788 – called "invasion day" by many Aborigines.

Abbott appeared to be the target of protesters, who chanted "shame" and "racist" outside the restaurant.

The Tent Embassy celebrated its 40th anniversary on Thursday and Abbott has angered indigenous activists by saying it is time the encampment "moved on".

Gillard was unharmed and hosted another Australia Day function at her official residence in Canberra later in the day.